An application of this invention is to carry RF signals between vertically stacked modules of RF components/circuits. Conventional techniques include interconnecting modules with coaxial cables with connectors, mating coaxial push=on coaxial connectors, soldered ribbons or soldered flexible cables. The disadvantages of these techniques include size, weight and assembly costs. Such connection techniques require several process steps. More permanent connections include the use of epoxies and solders. Moreover, direct vertical connections from coaxial line to three-wire transmission lines have the effect of exciting additional, undesirable waveguide modes within the module.